Charge Carrier Transport Characteristics of Quasi-1D Channel MOSFET Adopting Multi-Gate Structure

The shape of MOSFET channel can be modulated by the electrostatic band bending (field-induced doping) with the multiple gate electrodes biased independently. Here, we demonstrate the formation of quasi-1D channel in a planar Schottky barrier MOSFET with side and control gates. The MOSFET was fabricated on a mesa structure formed by etching the intrinsic silicon layer of a silicon-on-insulator (SOI) wafer with KOH to suppress the off-state leakage current. The finite-element electrostatic modeling was used to obtain the energy band profile and to find the quantized subband states in the quasi-1D channel, determining the distinctive features in the charge carrier transport of this device structure. Accordingly, the transfer curves (I_ds-V_g) of fabricated devices were measured in a wide temperature range of 5-300 K with the drain voltage (V_ds) being varied to investigate the temperature and bias dependences of quasi-1D transport. It was confirmed that the devices can operate as both n- and p-channel MOSFET (ambipolar). In the case of p-channel, the extracted subthreshold swings were estimated to be ~421 mV/dec at 300 K and ~57 mV/dec at 5 K, reflecting the transition from thermionic emission limited to tunneling dominant transport as temperature decreases. At low temperatures, the current plateaus were observed at sufficiently small V_ds (around 0.2 V), whereas the transconductance oscillation appeared in the same gate voltage region as for the current plateaus at even smaller V_ds. These observations are considered to signify clearly the quantum nature of charge carrier transport expected in such a confined channel.